On 13/12/2011 8:08 PM, Savas Piperidis wrote:
> I tried to use the Sparkfun BOB-08745 logic level converter (
> http://www.sparkfun.com/products/8745 http://www.sparkfun.com/products/8745
> ) to connect the serial port of my Gumstix Overo Fire COM to a 5V TTL level
> serial port. At my overo board I use the O0 serial port (pins 9, 10 of the
> 40 pin header connected to the TXI and RXO at the low voltage level side of
> the converter) and the VCC_1.8 and GND ( pins 26, 25 of the 40 pin header
> connected to the LV and GND at the low voltage side of the converter). At
> the high voltage side of the converter I connect the appropriate data and
> power signals of the 5V TTL serial port device. I double checked all the
> connections and I used the libserial C++ library and the minicom program for
> communication but, unfortunately, the connection is dead. It seems to work
> for receiving data from the device's 5V TTL serial port but it is not
> possible to send data from the Overo board. From the technical
> specifications of the Sparkfun BOB-08745 converter it seems that it is
> compatible with the signal levels of my devices. Has anybody some previous
> experience with this converter?
> I would also like to ask why at the /dev directory of my overo board exist
> the O0, O1, O2 ports that seems to work, but also exist the S0, S1, S2, S3
> ports that seems to be dead?
> For several days I tried everything I could think but the connection is not
> working. I have checked the 5V TTL serial port of the device, establishing a
> connection with my PC, through a ftdi usb to serial converter and it is
> working fine. The O0 serial port of my overo board is also working if I use
> a different connection than the one with the converter.
> Any Ideas?
> Savas Piperidis
We use the exact same sparkfun level converter for a serial connection
(root console) then a max232 chip then to a standard pc serial port.
We don't connect the low side ground to the level shifter, as the spark
fun level shifter board has a common ground.
We've done the same(not connect the low side ground) for spi and i2c
with the level shifters.
For i2c even though the boards have pullups builtin, we've found we need
4.7k ohm pullups
Which pins are you using ?
tx and rx or tx and tx ?
Scott Ellis has code and schematic on his site for i2c connections